The confusion exists because char** can be a couple of things in C you can't distinguish them without looking at the initialization code
1.) A pointer to a char* (always true)
2.) An array of char* (if initialized as such)
3.) A multidimensional char array (if initialized as such)
Number 3 in particular usually causes mass confusion with students learning C.
The typedef doesn't stop you assuming the wrong thing but it does give you language cues to what it is and is easier to read.
But this is not what I am looking for. I want to initialize, using fopen(), the ptrLogFile just once (may be in globals.h?) and then re-use it in file1.c and file2.c as long as I want. Finally close it in file3.c when the program is shutting down. How do I do this? Thanks
Don't do it that way. Create a function or library module that does all the work and then just call the actual logging functions anywhere in your code. Call the initialiser, to open the file, at the beginning of your main module, and the closing operation just before your main program terminates.
basically my problem is how to get rid of flickering when i use customdraw.
I know about double bufering, bckgnderase and any other solutions, but all of them do not work in my case, because my customdraw is called for each item (when resizing window(mfc behavior)) and for some of them when multiselection happens. CustomDraw is called from OnNotify(need that because i am extending normal tree with columns like in listView - so it look smth like Grid with expandable rows).
Cause of all that behavior that i need, got no idea how to apply double buffering into this, cause there's none notification when to bitblt offscreen bitmap into screen.
There double buffering technique that is fairly trivial to implement and gives reasonable results for any complex drawing
1.) Your draw routines only draw on a memory context, don't draw to the screen at all in those item draw calls.
2.) You use a standard windows timer which will timeout after a set time and you use that to update the screen.
3.) Anytime you draw to the memory context in step 1 you kill the running any timer and restart it
4.) The timer running out posts off a message and if you use that message to transfer the memory DC to screen, you then dispose of the timer.
You should be able to get what happens that each item simply draws itself to the memory DC and will restart the timer. When the last item has been drawn the timer will finally hit it's wait timeout and post off the message which will draw all the items together as one big bitblt draw and no flickering.
The requirements 1 memory context (created when window is created), 1 timer which is created and disposed as per above.
You should return true (being a non zero value) otherwise window will remain marked for erasing which somewhere down the track may come back to bite you. Remember the API underworkings aren't fixed you may find an old version of Windows or a new update which decides to use the flag.
In client application I created Private sensor pool using msdn demo code.
and using that code I'm able to open session enroll fingerprints.
But the problems are
1. When tried to enroll same fingerprint again then it causes to stop WbioSrvc so I need to restart my application again.
2. similar thing happening while identifying when trying to identify with random finger function working fine it is returning unknown identity. But when trying to saved fingerprint instead of identifying it is causing to stop WbioSrvc.